Many glaciers around the world are losing ice mass and retreating. One such area is the Southern Patagonia Icefield (SPI) in Chile. However, one glacier in the SPI is actually defying the worldwide trend. The Pio XI Glacier is advancing, and based on scientific studies, there is no clear reason why.

Pio XI flows from the SPI toward the west then splits into two fronts. From 1998 to 2014, the southern front advanced 593 meters. The northern front, which flows into Lake Greve, advanced 107 meters in the same time period. This pair of Landsat images shows that all of the other glaciers that flow down from the SPI into Lake Greve are retreating.

The complex behavior of glaciers involves more than just measuring where the ice ends. Scientists theorize that something is happening inside or beneath Pio XI to make it advance, rather than an external factor like climate. The glacier flows from a wide accumulation area into a narrow outlet, and the depth of the lakes it flows into, along with the speed of the glacier’s flow, may also be factors.

Whatever the cause, glaciers continue to be closely monitored, and in the remote region of the SPI, that monitoring needs to be done with remote sensing. Landsat offers several observations per year in these areas and will help scientists understand the glacier’s future behavior.